Polyoxometalate-catalysed epoxidation of 1-octene with hydrogen peroxide in microemulsions coupled with ultrafiltration

Epoxidation of 1-octene with hydrogen peroxide catalysed by amphiphilic salts of peroxo tungstophosphate [PO4[WO(O2)2]4]3- in water-in-oil microemulsions is an efficient and environmentally benign reaction which, coupled with ultrafiltration, shows the potential for continuous production of epoxides.     

An algorithm for the enumeration of spanning trees

Enumeration of spanning trees of an undirected graph is one of the graph problems that has received much attention in the literature. In this paper a new enumeration algorithm based on the idea of contractions of the graph is presented. The worst-case time complexity of the algorithm isO(n+m+nt) wheren is the number of vertices,m the number of edges, andt the number of spanning trees in the graph. The worst-case space complexity of the algorithm isO(n ²). Computational analysis indicates that the algorithm requires less computation time than any other of the previously best-known algorithms.     

Theory of free-electron optical absorption in n-GaAs

Free-electron optical absorption of Se-doped GaAs at room temperature is calculated and compared with existing experimental data. In addition to the standard features the theory takes into account a non-parabolic character of the conduction band, a short-range component of the Se donor potential and a plasmon generation in the presence of donors. Deformation potential constants for the conduction and the valence bands are calculated using the empirical pseudopotential method. A value of C = -15.7 eV is obtained for the conduction band and shown to agree with existing hydrostatic and uniaxial stress experiments. Assuming no impurity compensation and using no adjustable parameters we successfully describe the experimental free-electron absorption in GaAs as a function of photon wavelength for samples with various donor densities.     

Synthesis and study of the rate of aminolysis of O-(acylaminoacyl)oximes of formylpyridines and pyridyl methyl ketones

A number of O-(benzyloxycarbonylglycyl) derivatives of alkyl-, phenyl-, and pyridyl-substituted oximes were synthesized, and their chemical properties and reactivities under aminolysis conditions were studied. The principal factor that determines the reactivities of the investigated compounds during the formation of a peptide bond is the presence of a weakly acidic catalyst; the different reactivities of the compounds under the same conditions are due to the influence of the electron-acceptor effects of the substituents attached to the carbon atom of the oxime group.The authors thank the Polish Academy of Sciences for financial support (state subsidy MR 1.12.1.6.1.5).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1336–1339, October, 1977.     

On the existence of specified cycles in a tournament

For 2 ≦ p ≦n and n ≧ 3, D(n, p) denotes the digraph with n vertices obtained from a directed cycle of length n by changing the orientation of p- 1 consecutives edges. In this paper, we prove that every tournament of order n ≧ 7 contains D(n, p) for p = 2, 3, …, n. Furthermore, we determine the tournaments of order n, 3 ≦ n ≦ 6, which do not contain D(n, p) for some p.     

Dendrites and light open mappings

It is shown that a metric continuum is a dendrite if and only if for every compact space and for every light open mapping such that there is a copy of in for which the restriction is a homeomorphism. Another characterization of dendrites in terms of continuous selections of multivalued functions is also obtained.

     

Structure of 6-methyl-3,20-dioxo-4,6-pregnadien-17α-yl acetate,C24H32O4

The X-ray structure of 6-methyl-3,20-dioxo-4,6-pregnadien-17-yl acetate is reported. The crystals are monoclinic, space groupP2₁,Z=4,a=28.955(7),b=6.597(2),c=11.064(3) Å,/gb=90.80(2) °. The two crystallographically independent molecules have very similar overall geometries. The A rings have intermediate sofa-half-chair conformations and are bent relative to the steroid skeleton. The conformation of the 17-progesterone side chain is stabilized by the 17-ester substituent; the C(16)-C(17)-C(20)-O(20) torsion angle is –19.4(6) and –20.6(7)°.     

Activation of the Normal Human Skin Cells by a Portable Dielectric Barrier Discharge-Based Reaction-Discharge System of a Defined Gas Temperature

Skin injury leading to chronic wounds is of high interest due to the increasing number of patients suffering from this symptom. Proliferation, migration, and angiogenesis are key factors in the wound healing processes. For that reason, controlled promotion of these processes is required. In this work, we present the portable helium-dielectric barrier discharge (He-DBD)-based reaction-discharge system of controlled gas temperature for biological activities. To make this He-DBD-based reaction-discharge system safe for biological purposes, a multivariate optimization of the operating parameters was performed. To evaluate the effect of the He-DBD operating parameters on the rotational gas temperature T_rot(OH), a design of experiment followed by a Response Surface Methodology was applied. Based on the suggested statistical model, the optimal operating conditions under which the T_rot(OH) is less than 37 °C (310 K) were estimated. Then, the resulted model was validated in order to confirm its accuracy. After estimation the optical operating conditions of He-DBD operation, the spectroscopic characteristic of the He-DBD-based reaction-discharge system in relevance to the several optical temperatures in addition to electron number density has been carried out. Additionally, the qualitative and quantitative analyses of the reactive oxygen species and reactive nitrogen species were performed in order to investigate of reactions and processes running in the He-DBD-gaseous phase and in the He-DBD-treated liquid. Next, the developed portable He-DBD-based reaction-discharge system, working under the optimal operating conditions, was used to stimulate the wound healing process. It was found that a 30 s He-DBD treatment significantly increased the proliferation, migration, and angiogenesis of keratinocytes (HaCaT) and fibroblasts (MSU-1.1) cell lines, as well as human skin microvascular endothelial cells (HSkMEC.2). Hence, the application of the cold atmospheric pressure plasma generated in this He-DBD-based reaction-discharge system might be an alternative therapy for patient suffering from chronic wounds.